Name of research institute or organization: Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Umweltmineralogie

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$Name of research institute or organization: Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Umweltmineralogie Title of project: Identification of the ice forming fraction$

1 Name of research institute or organization: Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Umweltmineralogie Title of project: Identification of the ice forming fraction of the atmospheric aerosol in mixed-phase clouds by environmental scanning electron microscopy Project leader and team: Prof. Stephan Weinbruch, project leader Dr. Martin Ebert, Dr. Anette Worringen, Dr. Nathalie Brenker Project description: The main focus of this experiment was the study of aerosol-cloud interaction processes in mixed-phase clouds. The high altitude research station Jungfraujoch enables the unique feature for ground-based in situ sampling of mixed phase clouds. Our main focus was to identify the ice forming fraction of the total aerosol in mixedphase clouds. Most particles in the interstitial aerosol fraction were found to be carbon dominated, some are internally mixed with sulphates, nitrates, and/or silicates. For the ice crystal residuals we have found two maxima in the size distribution, one above and one below 1 µm. The smaller particles (< 1 µm) show a similar elemental composition as the interstitial particles, except that internal mixtures of nitrates and sulphates are less frequent. Above 1 µm additionally external silicates (soil material) are a main component. The observation that silicates are well suited to act as ice nuclei, while sulphate- and nitrate-particles (at the Jungfraujoch often observed as internal mixtures or coatings of carbon dominated particles) remain in the interstitial fraction is in good agreement with the results of other studies and our co-workers. Motivation In February/March 2004 an intensive Cloud and Aerosol Characterization Experiment (CLACE-4) was conducted at the high alpine research station Jungfraujoch (JFJ, 3580 m asl; o N, 7.98 o E) in Switzerland. The main focus of this experiment was the study of aerosol-cloud interaction processes in mixed-phase clouds. The high altitude research station Jungfraujoch enables the unique feature for ground-based in situ sampling of mixed phase clouds. 105

$1 µm) linked with two different inlet systems for the sampling of different fractions of the aerosol particles inside the mixed-phase clouds.$ Impactor housing jets substrate holder Figure 1: Self-constructed two-stage mini-cascade impactor (length ~ 8cm) for the sampling of ice nuclei and interstitial aerosol (in combination with the

Impactor housing jets substrate holder Figure 1: Self-constructed two-stage mini-cascade impactor (length ~ 8cm) for the sampling of ice nuclei and interstitial aerosol (in combination with the

2 Sampling For this purpose, we have used two self constructed miniaturized two stage impactors (cut off diameter 1.8 µm and 0.1 µm) linked with two different inlet systems for the sampling of different fractions of the aerosol particles inside the mixed-phase clouds. Impactor housing jets substrate holder Figure 1: Self-constructed two-stage mini-cascade impactor (length ~ 8cm) for the sampling of ice nuclei and interstitial aerosol (in combination with the described inlet systems). First, for the sampling of the interstitial aerosol an interstitial inlet operated with a PM2 cyclone impactor was used. Second, we have used an ice-cvi (Counterflow Virtual Impactor) inlet, which was designed at the Institute for Tropospherical Research (IfT) in Leipzig, Germany (Mertes et al., 2005) to sample residual particles of small ice crystals (IN). Results and discussion The size, morphology and elemental composition of some hundred particles of selected interstitial- and IN- samples will be analyzed by environmental scanning electron microscopy (ESEM) combined with energy dispersive X-ray analysis (EDX). Because of the use of nickel plates as impaction substrates, also hygroscopicity and volatility investigations are enabled by ESEM. Final results of the individual particle analysis of the CLACE-4 campaign cannot be presented at this time, but our preliminary results show the same trends as we have found in the CLACE-3 campaign at the Jungfraujoch station, in which we participated in During CLACE-3 the interstitial aerosol shows a maximum in the size distribution in the range of nm. Most particles are carbon- 106

3 dominated, sulphates, or mixtures of sulphates with nitrates, carbon-dominated particles or silicates. Figure 2: TEM brightfield image of sulphate droplets in an interstitial sample of the CLACE-4 campaign. a b Figure 3: Secondary electron images of ice crystal residuals (IN): (a) silicatic soil material; (b) carbon-dominated particles (images from the CLACE-3 campaign). 107

Figure 4: Silicon- (green) and carbon- (blue) element distribution images, derived by EDX mapping in the ESEM, superimposed to the referring secondary electron image of an IN sample (CLACE-3: cloud

4 Figure 4: Silicon- (green) and carbon- (blue) element distribution images, derived by EDX mapping in the ESEM, superimposed to the referring secondary electron image of an IN sample (CLACE-3: cloud event 13, March 21, 2004 March 22, 2004). This false colour mapping identifies some external silicates and carbon rich particles besides a majority of internal mixed carbon/silicate particles. For the ice crystal residuals we have found two maxima in the size distribution, one above and one below 1 µm. The smaller particles (< 1 µm) show a similar elemental composition as the interstitial particles, except that internal mixtures of nitrates and sulphates are less frequent. Above 1 µm additionally external silicates (soil material) are a main component. 108

Table 1: Particle group abundances [%] in three mixed cloud events for the ice-nuclei (IN) and for the

There are two characteristics in particle composition during the CLACE-4 experiment in contrast to the CLACE-3

Firstly, there is a high abundance of irregular shaped aluminium oxides and mostly spherical calcium fluorides at

$Secondly, externally mixed silicates are also found in the interstitial fraction during CLACE-4, which was also$ not the case during CLACE-3 (see Table 1).

not the case during CLACE-3 (see Table 1).

5 Table 1: Particle group abundances [%] in three mixed cloud events for the ice-nuclei (IN) and for the interstitial aerosol particles during CLACE-3. There are two characteristics in particle composition during the CLACE-4 experiment in contrast to the CLACE-3 campaign. Firstly, there is a high abundance of irregular shaped aluminium oxides and mostly spherical calcium fluorides at some days, which were not detected in these concentrations during CLACE-3. These particle groups have no strong natural source in this region and are probably a sampling artifact. Secondly, externally mixed silicates are also found in the interstitial fraction during CLACE-4, which was also not the case during CLACE-3 (see Table 1). Maybe these particles have to be traced back to the rock blastings, which were done near the Jungfraujoch station during the whole campaign. For this reason, we are very thankful that it was possible to realize a stop of these blastings during the CLACE-5 campaign in Figure 5: Secondary electron images of ice crystal residuals (IN): (left) Calcium fluoride spheres; (right) aluminium oxide particle. 109

6 The observation that silicates are well suited to act as ice nuclei, while sulphate- and nitrate-particles (at the Jungfraujoch often observed as internal mixtures or coatings of carbon dominated particles) remain in the interstitial fraction is in good agreement with the results of other studies and our co-workers. The source of the in the INfraction most abundant particle group, the carbon dominated -particles is not completely solved. EDX allows only the detection of carbon, not the classification as organic or elemental carbon. Based on morphology only single particles in the interstitial- and IN-fraction could definitely be identified as soot. Additional experiments in the ESEM showed no visible water uptake of the carbon dominated particles at a relative humidity of 95% and no volatilization of these particles, even at 300 C and a water vapor pressure of 1.3 mbar. Because of these result and the fact that an aerodyne aerosol mass spectrometer could not measure any significant organic signals in the IN-fraction it can be assumed that the carbon dominated particles, which were found in the IN-fraction, consist neither of highly volatile organics, nor of elemental carbon, but of low-volatility organics. One possible source for these particles could be found in oil combustion. References S. Mertes, B. Verheggen, J. Schneider, M. Ebert, S. Walter, A. Worringen, M. Inerle- Hof, J. Cozic, M.J. Flynn, P. Connolly, K.N. Bower, E. Weingartner, Sampling and physico-chemical characterisation of ice nuclei in mixed phase clouds at the high alpine research station Jungfraujoch (3580 asl) during CLACE, Journal of Aerosol Science, Abstracts of EAC, Ghent, 2005, S130. M. Ebert, M. Inerle-Hof, S. Mertes, S. Walter, J. Schneider, B. Verheggen, J. Cozic, E. Weingartner, and S. Weinbruch, Identification of the ice forming fraction of the atmospheric aerosol in mixed-phase clouds by environmental scanning electron microscopy, Journal of Aerosol Science, Abstracts of EAC, Ghent, 2005, S504. Key words: Ice nuclei, ESEM, individual particle analysis, chemical composition Collaborating partners/networks: Institute for Tropospherical Research, Leipzig, Germany Scientific publications and public outreach 2005: Conference papers J. Cozic, E. Weingartner, B. Verheggen, S. Sjögren, J. Duplissy, J.S. van Ekeren, U. Baltensperger, S. Mertes, K.N. Bower, M. Flyn n, P. Connolly, J. Allan, J. Crozier, M. Gallagher, H. Coe, S. Walter, J. Schneider, N. Hock, J. Curtius, S. Borrmann, A. Petzold, S. Henning, Thomas Rosenørn, M Bilde, M. Ebert, M. Inerle-Hof, A. Worringen, S. Weinbruch, E. Fries, W. Püttmann, W. Jaeschke, P. Aalto, A. Hirsikko, M. Vana, M. Kulmala, Aerosol Cloud Interaction: Highlights From The Cloud And Aerosol Characterization Experiments (Clace) Conducted At The High Alpine Research Station Jungfraujoch In Switzerland, Accent Conference In Urbino In September E. Weingartner, B. Verheggen, J. Cozic, S. Sjögren, J.Duplissy, J.S. van Ekeren, U. Baltensperger, S. Mertes, K.N. Bower, M. Flynn, P. Connolly, J. Crozier, M. Gallagher, H. Coe, S. Walter, J. Schneider, N. Hock, J. Curtius, S. Borrmann, A. Petzold, S. Henning, Thomas Rosenørn, M Bilde, M. Ebert, M. Inerle-Hof, S. Weinbruch, E. Fries, W. Püttmann, W. Jaeschke, P. Aalto, A. Hirsikko, M. Kulmala, 110

7 An overview of the Cloud and Aerosol Characterization Experiments (CLACE) conducted at the high alpine research station Jungfraujoch in Switzerland, Journal of Aerosol Science, Abstracts of EAC, Ghent, 2004, S129. Weingartner, E., B. Verheggen, J. Cozic, S. Sjögren, J.S. van Ekeren, U. Baltensperger, S. Mertes, K.N. Bower, M. Flynn, J. Crozier, M. Gallagher, H. Coe, S. Walter, J. Schneider, N. Hock, J. Curtius, S. Borrmann, A. Petzold, M. Ebert, M. Inerle-Hof, S. Weinbruch, An overview of the Cloud and Aerosol Characterization Experiments (CLACE) conducted at a high alpine site in the free troposphere, EGU Ebert, M., M. Inerle-Hof und S.Weinbruch, Untersuchungen von Residuen von Eiskristallen sowie des Prozesses der Eiskeimbildung in einem Environmental Scanning Electron Microscope (ESEM), the second workshop Die troposphärische Eisphase TROPEIS II, Frankfurt, Mertes, S., A. Schwarzenböck, J. Schneider, S. Walter, M. Ebert, M. Inerle-Hof, B. Verheggen, J. Cozic und E. Weingartner, Ein Counterflow-Virtual Impactor (CVI) System zur Sammlung frisch gebildeter Eispartikel in Mischphasenwolken auf der hochalpinen Forschungsstation Jungfraujoch (3580 m): Funktionsweise und erste Ergebnisse des ICE-CVI, the second workshop Die troposphärische Eisphase TROPEIS II, Frankfurt, Weingartner, E., B. Verheggen, J. Cozic, S. Sjögren, S. van Ekeren, N. Bukowiecki, U. Baltensperger, S. Mertes, K.N. Bower, M.J. Flynn, J.D. Allan, M.W. Gallagher, J. Crosier, H. Coe, T.W. Choularton, J. Schneider, S. Walter, S. Henning, T. Rosenhørn, M. Bilde, A. Petzold, M. Inerle-Hof, M. Ebert, S. Weinbruch, Wintermesskampagne CLACE-3 auf dem Jungfraujoch (3580 m.ü.m.) im Überblick, the second workshop Die troposphärische Eisphase TROPEIS II, Frankfurt, Mertes, S., A. Schwarzenböck, J. Schneider, S. Walter, M. Ebert, M. Inerle-Hof, B. Verheggen, J. Cozic, and, E. Weingartner, Design and Operation of a Counterflow Virtual Impactor Inlet System to Collect Small Ice Particles out of Mixed Phase Clouds at the High Alpine Site Jungfraujoch (3580 M Asl), Journal of Aerosol Science, Abstracts of EAC, Volume I, Budapest, 2004, S Verheggen, B., J. Cozic, E. Weingartner, S. Sjögren, S. Van Ekeren, N. Bukowiecki, R. Schmidhauser, U. Baltensperger, S. Mertes, K. N. Bower, M. J. Flynn, J. D. Allan, M. W. Gallagher, J. Crosier, H. Coe, T. W. Choularton, J. Schneider, S. Walter, S. Henning, T. Rosenørn, M. Bilde, A. Petzold, E. Barthazy, M. Inerle-Hof, M. Ebert, and S. Weinbruch, Clace-3: Third Cloud and Aerosol Characterization Experiment Conducted at a High Alpine Site in The Free Troposphere, Journal of Aerosol Science, Abstracts of EAC, Volume I, Budapest, 2004, S S. Mertes, B. Verheggen, J. Schneider, M. Ebert, S. Walter, A. Worringen, M. Inerle- Hof, J. Cozic, M.J. Flynn, P. Connolly, K.N. Bower, E. Weingartner, Sampling and physico-chemical characterisation of ice nuclei in mixed phase clouds at the high alpine research station Jungfraujoch (3580 asl) during CLACE, Journal of Aerosol Science, Abstracts of EAC, Ghent, 2005, S130. M. Ebert, M. Inerle-Hof, S. Mertes, S. Walter, J. Schneider, B. Verheggen, J. Cozic, E. Weingartner, and S. Weinbruch, Identification of the ice forming fraction of the atmospheric aerosol in mixed-phase clouds by environmental scanning electron microscopy, Journal of Aerosol Science, Abstracts of EAC, Ghent, 2005, S

8 Address: Dr. Martin Ebert TU-Darmstadt Institut für Angewandte Geowissenschaften Fachgebiet Umweltmineralogie Schnittspahnstr Darmstadt Contacts: Dr. Martin Ebert Tel.: 06151/ Fax: 06151/ mebert@geo.tu-darmstadt.de 112

Name of research institute or organization: Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Umweltmineralogie

Name of research institute or organization: Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Umweltmineralogie Title of project: Single particle analysis of ice nuclei and interstitial